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The final frontier gets a little closer

UVA grad student Xinlun Cheng has mapped the warped outer edges of the Milky Way, shown here, with great precision. Xinlun Cheng

Recent research is giving us a better sense of our galaxy and the rest of the universe. Here at UVA, scientists are getting a more accurate picture of a warp in the outer part of the Milky Way. You might visualize it, says astronomy graduate student Xinlun Cheng (Grad ’26), like a stadium wave, moving around the edge of the galaxy just like you’d see move through the crowd of fans at a football game. But in this case, the crowd is stars, and the stars are rotating around the center of the galaxy.

Researchers have known about the wave for a while, but thanks to new data from some advanced observation instruments, “We were able to map out where the stars are and how they are moving with incredible precision,” says Cheng, who served as lead author on the report published on the team’s findings in The Astrophysical Journal. What caused the warp in the first place is uncertain; one theory is that it might have been caused by the gravitational pull from a smaller galaxy passing nearby billions of years ago. Interestingly, however, Cheng notes that their findings also indicate that the warp is rotating at a different speed from the galaxy itself. Previous researchers have suggested the possibility, but, says Cheng, “for the first time we managed to reveal this with very high accuracy.”

Taking a much bigger-picture look, UVA visiting professor of astronomy Anatoly Klypin was part of an international research effort to calculate the total amount of matter in the universe. 

But Klypin explains that while their work concluded that matter makes up 31.5 percent of all the matter and energy in the universe, the importance of these calculations is less about the numbers themselves than about what they might help tell us about the nature of the universe. 

Most of the mass of the universe—the other 68.5 percent that isn’t matter—is a still-undefined component scientists refer to as “dark energy,” which neither emits nor absorbs light, explains Klypin, and even much of the matter itself isn’t the stars and gases and familiar stuff we are made of but rather an unknown component called “dark matter.” 

But the more accurately we can measure what we do know, the more we can constrain what we don’t—the nature of dark matter, dark energy, and the universe itself. “We get our experience, our common sense, from normal life,” says Klypin, “and normal life is definitely different from what the whole universe is doing.”